Communications

The Communication subsystem is responsible for enabling half-duplex communication of the satellite with various ground stations in the HAM band of 434-438 MHz which is used both for up-linking and down-linking data. The frequency used by satellite will be 437.025 MHz.
The half-duplex communication of the satellite with a ground station is done through text messages when a valid link is established with a ground station whereas the beacon containing status of various important components of all the subsystems of the payload is autonomously transmitted by the satellite at regular intervals of time. Additionally, the aim of the communication system is to characterize the UHF channel in a LEOS orbit, to map the packet error rate with respect to the transmitted power for the optimal utilization of bandwidth.

System Design:
The subsystem consists of the amplifiers (LNA & HPA), the antenna, the transceiver and the terminal node controller at the payload and ground station.

Ground Station (VU2COE): In addition to above mentioned parameters, subsystem consists of the satellite tracking system at the ground station which includes an antenna rotor system and a 2 unit crossed Yagi-Uda antenna. The ground station is located in the college premises, and beacon reception from some satellites is done on a regular basis. We also have successfully communicated with International Space Station using APRS.

Payload Communication System: The transceiver receives the signals from the antenna after passing through the amplifiers. The terminal node controller then does error checking of the received data. If the received data is error-free, it is forwarded to the on board computer that stores the received data against the respective ground station. The same sequence of processes take place in reverse direction while down-linking from the satellite.

Current Work:

Communications payload board

1. Line of Sight Communication link has been established with the Ground Station hardware.

>2. Regular testing and maintenance of the ground station equipments and setup.

Ground Station News:

1. Ground station has been successfully set up (an in-house built 2 unit crossed Yagi-Uda antenna mounted on a rotor system, controlled by a satellite tracking software).

2. Successfully communicated with International Space Station using APRS.

3. Completed design and testing of payload board.

4. Satellite and Ground Station Antennas have been optimized.

5. Received digital data from satellites operating in the HAM band and got the data verified from the corresponding satellite teams.